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Old 03 July 2012, 05:12   #1
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Country: Ireland
Town: galway
Make: Scorpian
Length: 9m +
Engine: Yamaha 420 STI
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hydradrive prop advice

Hey Guys,
I need a prop for my yamaha hydradrive unit, im running a 4.2l yamaha 420sti in a 9m scorpion rib, what are my options? does it have to be a genuine hydradrive prop or would would the likes of a solas do it? also does anybosy know the dimensions of the required prop, diameter? some listings say 14'' some say 19''...
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Old 03 July 2012, 18:02   #2
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Boat name: Lunasea
Make: Ribtec 890SX
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I have a large selection of Mercury props from my offshore days and they physically fit on the Hydradrives. You may new to play with spacers for the depth on the hub but I have a bucketful of them.

Too bad you are not in Sydney I could have lent you some. Actually you wouldn't want to be here, it is the middle of winter and we are only getting about 17 degrees today.
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Old 03 July 2012, 18:09   #3
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Country: UK - England
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Its the middle of summer here and we would be lucky to see 17'......just misery :'(
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Old 03 July 2012, 18:25   #4
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Country: Ireland
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props

well its the middle of summer here too and its bucketing down, however...... its the finale of the volvo ocean race so the town and sea is buzzing! I need a prop fast! Would you happen to know what other brands physically fit also? I tried a solas 14.5 inch by 21 degree last night but its way under propped.
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Old 03 July 2012, 22:18   #5
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Country: Australia
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V6 Suzuki outboard, V6 Yamaha outboard, mercury V6 outboard, mercury alpha or bravo 1 will all physically fit.

As for pitch size, I can't advise you but there should be a number on your old prop. I think it is on the hub between the blades. Remember that a 3 blade prop will need to be 1 or 2 inches more pitch to get the same speed. My 9 meter with twin 421's has 21 inch pitch I think. With one engine, maybe you need a 19 or less.

Over propping, too high a pitch, can melt a piston or 2 so whatever prop you get just make sure you can get max rpm when fully loaded.

There is a whole science to props depending on if your boat needs lift in the back or not and how you use your boat as well as what height your sterndrive has been set at.

In my opinion the standard Hydradrive props are a pretty good option.
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Old 03 July 2012, 22:19   #6
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Just read that a 21 was under propped. Wow! Keep going up in numbers till its right. Just make sure you can get max rpm fully loaded.
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Old 04 July 2012, 03:47   #7
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Quote:
Originally Posted by kubcat View Post
Just read that a 21 was under propped. Wow! Keep going up in numbers till its right. Just make sure you can get max rpm fully loaded.

Yes, i had it fully loaded with fuel and people, however that 21 degree pitch was on a solas 14.5 inch diameter prop which I now know is too small, as far as I can determine I need a 17 inch diameter.
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Old 04 July 2012, 12:35   #8
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Country: UK - Scotland
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Make: Parker 750 CC
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Hydra Drive Prop

I have a new 16x3/8x23 hydra drive propeller as the attached pictures.

The Redbay Stormforce RIBs used:

21 or 23 on the 7.4mtr
19 or 21 on the 8.4mtr

I would think you would need a 19 I would have a word with Steel Developments regarding the options open to you (020 8874 7059).
All the best Callum.
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Old 05 July 2012, 10:13   #9
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Hi Callum, how much are you looking for for that prop?
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Old 05 July 2012, 11:55   #10
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I paid 800 for it new, I would take 400.
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